1. Field of the Invention
The present invention relates to the hand mixing of cement and like compounds that include different components (e.g. a solid component and a liquid component) that mix together and rapidly harden. Even more particularly, the present invention relates to an improved method and apparatus for hand mixing bone cement components wherein a common hollow base receptacle accepts either a mixing bowl or a mixing syringe within an enclosure that is defined by the hollow base receptacle and a lid.
2. General Background
Devices for mixing cement are well known in the art. For many years, various compounds and resins such as bone cement, dental mixtures and the like have been mixed in a container and subjected to a vacuum for removing the air bubbles contained within the cement. The Whip Mix Corporation sold a product in the 1960's known as the "Vac-u-Vestor" that included a vacuum pump for generating a working vacuum in combination with a mixer in a short period of time. Various patents have issued for vacuum mixers that are used to mix cement and the like.
The Frankel U.S. Pat. No. 4,015,945 provides a mixer, for a volatile substance that emits a noxious vapor, that prevents vapors from escaping into the atmosphere. The mixer is made of an outer bowl, open at the top, with an exhaust port in the side. It has a means to connect the exhaust port to a vacuum source. It has a replaceable (disposable) bowl liner, open at the top, that fits into the outer bowl, and spacers that permit fluid flow between the bowl and liner. The liner has several exhaust holes around the open end. The mixer further has a deflector cap that funnels air into the mixer yet permits hand access to the liner for stirring the cement.
The Puderbaugh U.S. Pat. No. 4,185,072 discloses a mixer, for a substance that produces gaseous reaction products, that evacuates the reaction products. The mixer has an outer bowl, open at the top, with an exhaust port in the side that connects to an exhaust means. It has a bowl shaped liner that fits in the outer bowl. Fluid flow is possible between the liner and the outer bowl through at least one vent in the liner, a space between the liner and housing, and the exhaust port. The mixer has a removable top that seals the mixer and keeps gases inside. The top has a mixing paddle acting through it with several open-center arms. At least one of the arms touches the wall of the liner. A crank on the outer side of the top permits rotation of the paddle.
The Solomon U.S. Pat. No. 4,277,184 provides a disposable, plastic, closed-system cement mixer. It consists of a cement cartridge with a barrel and a neck. The piston of the cartridge contains the mixing device. The paddles can move axially out of the piston and they can rotate to mix the cement. The mixer may also include an exhaust port for connection to an external vacuum source.
The Tepic U.S. Pat. No. 4,463,875 discusses a method of preparing and applying bone cement, where the two parts of the cement are vacuum packed in separate, flexible watertight containers. The two containers are abutted along the same axis and mixing takes place when one of the compartments is collapsed into the other. The mixture is then extruded from one chamber to the other several times until mixing is complete. The cement can be extruded by attaching a nozzle in place of one empty chamber.
In U.S. Pat. No. 4,671,263 there is disclosed a bone cement mixing and delivery system with a cylindrical cartridge, a plunger, a cap, a pressurizing unit, and a vent for exhausting the air entrapped in the cement. The system applies pressure to the cement prior to injection and vents the air and gases that separate from the bulk cement.
The Lidren U.S. Pat. No. 4,721,390 discusses a method of mixing bone cement in a mixing space designed to minimize air incorporation. A chilling of the monomer to 2.degree. to 6.degree. C. before mixing is discussed, and applying vacuum before mixing. A mixing of the cement in an operating room where the air and gases are drawn off and exhausted is disclosed by injecting the cement through a syringe and nozzle and injecting the cement under vacuum. The cement is also mixed in the syringe under vacuum.
The Gunnarson U.S. Pat. No. 4,758,096 provides a vacuum cement mixer with an outer vacuum chamber and inner mixing chamber, that connects to an external vacuum source. The mixing chamber has a piston and mixing takes place on top of the piston while vacuum exists on both sides of the piston. The mixer has a hand crank for mixing the cement. The paddle is perforated and scrapes the sides of the mixer.
The Bakels U.S. Pat. No. 4,787,751 provides a bone cement mixer with a cylindrical housing mounted on a plate with a vibrator. A cartridge fits inside the housing to hold the cement. The cartridge is subjected to vacuum and the housing, plate and cylinder are vibrated to mix the cement.
The Tepic U.S. Pat. No. 4,808,184 provides a method of preparing bone cement where the powder is supplied in a partially evacuated chamber and the liquid comes in another chamber. The two containers are joined with an airtight seal and the liquid is pressurized into the powder.
The Ziemann U.S. Pat. No. 4,854,716 provides a cement mixer with a container, a stirrer, a motor for driving the stirrer, a vacuum pump, and a controller for the motor and pump that includes a timer and a buzzer/signal.
The Draenert U.S. Pat. No. 4,966,601 provides a bone cement mixer with a container, a pressurizing device, a vent to release gases from the cement, an evacuating device to exhaust gases, and a means to retain the pressurized cement in the container. The Chan U.S. Pat. No. 4,973,168 provides a cement mixer with a cartridge containing the powder under vacuum, a separate container for the monomer, and a means of passing the monomer into the powder container.
The Draenert U.S. Pat. No. 5,015,101 provides a bone cement mixer with a cylindrical outer container and a cylindrical cartridge fitted with a flange that seals between the cartridge OD and the outer container ID. As the inner cartridge is forced into the outer container, mixed cement extrudes from the outer container into the inner cartridge. A mixing method is disclosed where the cement components are repeatedly pushed from one container to another.
The Tepic U.S. Pat. No. 5,051,482 provides a method of mixing bone cement where the powder is completely evacuated, then flooded with monomer. Excess monomer is drained off. Specific powder morphologies and formulations are disclosed.
The Chan U.S. Pat. No. 5,100,241 provides a cement mixing device where the powder is in an evacuated cartridge. The liquid monomer is introduced into the cartridge through a sealable connection.
The Kindt-Larsen U.S. Pat. No. 5,114,240 provides a method of mixing bone cement where the liquid is forced into the interstices between the powder particles.
The Planck U.S. Pat. No. 5,145,250 provides a method of producing bone cement in a device consisting of a sterile cartridge, stirrer, and automatic controller. Data on the type and quantity of cement is encoded on the cartridge. Inserting the cartridge into a holding apparatus allows the data to be read by an automatic controller. The automatic controller charges the cartridge with the correct cement components and mixes them automatically. An automatic resting phase follows. Reduced pressure in the mixing chamber is possible during at least part of the cycle. Further disclosures relate to exhausting gases from the mixer, filtering entering and exhausting air, chilling the cement components, storing cement components in bulk and dispensing them into the cartridge at surgery, monitoring temperatures and adjusting mixing accordingly, and controlling the temperature of the mixing cartridge.
The Faccioli U.S. Pat. No. 5,193,907 provides a method of mixing bone cement where the two components are kept in separate chambers within the same container until needed. The container for the liquid component is opened within one chamber, which is sealed from the atmosphere. Drawing a vacuum in the powder chamber causes the liquid to be sucked into the powder chamber. Agitation of the container causes mixing and compression of the cement extrudes it out of the container.
The Nilson U.S. Pat. No. 5,252,301 provides a bone cement mixer with a mixing cylinder where the bottom can move relative to the lid. The mixer has a perforated stirrer that can move axially in the cylinder, and mixing takes place under vacuum. The mixer also serves as a dispenser through a hollow tube.
The Nelson U.S. Pat. No. 5,265,956 provides a cement mixing chamber, a cartridge that attaches to the mixing chamber, and a passageway between the chamber and the cartridge. The chamber's outlet is initially sealed by the piston for the cartridge and there is a rod that pushes the piston into the cartridge when desired. The piston fits tightly in the mixing chamber outlet and slides easily in the cartridge. The rod is inside a hollow shaft which holds the mixing paddles in the mixing chamber. All points of communication between the mixing chamber and the outside are sealed to prevent air entering the mixing chamber.